What is a hyperthreading CPU?

Question

I am studying for my A+ cert test and I came across hyperthreading and I just don't understand what it is? I have read the wiki for it but it didn't explain exactly what it is?

Firstly what is a thread?
Secondly what is hyperthreading?

Answer 1

A thread is a sequence of commands that the processor can execute. Hyperthreading means that the processor can execute several threads at the same time.

Answer 2

A thread is contained inside a process. Multiple threads can exist within the same process and share resources such as memory. Your processor has to change between these threads to keep the processes (programs) running. The more the threads - the more the time it takes for the processor to process them.

Hyperthreading is a feature some Intel Pentium 4 processor and newer processors like i5 and i3 have (not 100% sure about it). Hyperthreading makes the switching between threads faster and altogether keeping the processes maintained better. Hyperthreading used to exist on single-cored processors, but now it has also been used in dual-core processors. It is also known as virtual core.

Answer 3

A thread is an asynchronous process operating on a computer. Asynchronous means that is does not execute in-step with the rest of the processes - it is independent and can run in the background if it needs to.

In an Operating System, virtual threads are used where a program can seemly operate on its own thread, but in reality it's still being multiplexed in time (see sources for muxing) with the rest of the system. You may have thousands of these running at any one time.



You can notice a thread if - for example - you made a Video Editing program render a video, but you're still able to use the program and press buttons while it works. This is because the render is executing on a separate thread.



Hyperthreading is the ability for one processor core to operate more than one thread. Each core is able to run asynchronously, but if each core can run 2 asynchronous threads or more, it is known as Hyperthreaded. A modern-day example of this is a second-generation Intel Sandy Bridge processor such as the i7-2600 where 4 cores with 2 threads each mean it can realistically run 8 real threads for every single clock cycle.

Answer 4

In laymans terms Hyperthreading capability of a CPU indicates it's ability to momentarily do "something else" while it's waiting for something to happen, most typically that alternate "thread" is executed while the CPU is waiting for a hard drive to finish a Seek/read/write operating.



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